BICM-ID (Iterative decoding processing: Bit Interleaved Coded Modulation with Iterative Decoding) method is a method in which a demodulator and a decoder perform iterative decoding through interleave processing that randomly rearranges the sequence of information bits, and deinterleave processing that returns the sequence of information bits, thereby performing MAP (Maximum a posteriori probability) decoding.
In recent years, there is proposed a technique for analyzing the convergence of iterative decoding processing, which is called EXIT (Extrinsic Information Transfer) analysis. The following becomes clear. In other words, even when each of an encoding method and a modulation method in the BICM-ID is not superior in single-body characteristics, the encoding method and the modulation method exhibit excellent decoding characteristics as a whole by properly matching both of the methods to each other.
Patent literature 1 discloses a method in which extended mapping that assigns bits, the number of which is greater than the number of bits that can be originally mapped, is combined with iterative encoding to achieve excellent characteristics. Patent literature 2 discloses a method that uses regular extended mapping in which while extended mapping is provided with certain regularity to reduce the computation amount, the extended mapping is matched to iterative encoding, thereby enabling to achieve excellent characteristics.
In these BIDM-ID methods, in general, bit likelihood information is exchanged between a demodulator and a decoder to perform iterative decoding processing. Therefore, interleave processing that randomly rearranges the sequence of bits between the demodulator and the decoder, and deinterleave processing, are performed in units of blocks into which a fixed number of bits of bit likelihood information are collectively grouped. The demodulator and the decoder subject bit likelihood information of the same block to demodulation processing and decoding processing respectively.
Meanwhile, with respect to wireless communication methods, as shown in non-patent literature 1 and non-patent literature 2, there is a method in which block-type interleaving and convolutional interleaving are used in combination as interleave processing